0

I have a for loop with a range of 2000 in this for loop I have to create an array called Array out of two other arrays, let's call them ArrayOfPositionSatellite with a size of (3,38) and the other array called ArrayOfPositionMassPoint with a size of (38, 3, 4412). The size of Array is (38,3,4412) and the size of PositonOfSatellite and PointsOfMassPoint is (3, ). My attempt to overwrite the ArrayOfMassPoint with to for-loops :

ArrayOfPositionSatellite=  ArrayOfPositionSatellite.T  
Array = ArrayOfPositionMassPoint
for  i in range(38):
     for k  in range(4412):
            PositionOfSatellite =  ArrayOfPositionSatellite[:,i]
            PositionOfMassPoint=  ArrayOfPositionMassPoint[i,:,k]
            ElementOfA = -Gravitationalconstant* (PositionOfSatellite  - PositionOfMassPoint)/(np.linalg.norm( PositionOfSatellite - PositionOfMassPoint)**3)
            Array[i,:,k] = ElementOfArray

Problem

My problem is that it takes around 3 hours to run the code and this is too long. Is there some way to make it more time-efficient?

If something is unclear please leave a comment and I will add more details.

MaxHuber1234
  • 21
  • 4

1 Answers1

4

You can vectorize your calculations. Like:

import numpy as np
ArrayOfPositionSatellite = np.random.randn(3, 38)
ArrayOfPositionMassPoint = np.random.randn(38, 3, 4412)
Gravitationalconstant = 6.67430e-11

# This is the difference vector
v = ArrayOfPositionMassPoint - ArrayOfPositionSatellite.T[:,:,None]
# This is norm of the difference vector
norm = np.linalg.norm(v, axis=1) ** 3
# This is normalized vector
norm_v = v / norm[:, None, :]
# This is the result
array = norm_v * -Gravitationalconstant
array.shape
>>> (38, 3, 4412)

This takes around ~40ms on my machine, instead of 3 hours.

armamut
  • 1,087
  • 6
  • 14